This invention relates to an improved molten metal spray forming atomizer, and more particularly to such an atomizer particularly adapted for spray forming of a refined molten metal from a molten metal refining or melting chamber. A molten metal spray forming atomizer is employed to convert a small molten metal stream from the melt chamber into an expanding metal spray or plume of small molten metal droplets which impinge and deposit on an appropriate collector to provide a large metal billet or other object of desired metal characteristics.
One example of molten metal refining is referred to as electroslag refining, and is illustrated and described in U.S. Pat. No. 5,160,532--Benz et al, assigned to the same assignee as the present invention.
In an electroslag process, a large ingot of a preferred metal may be effectively refined in a molten state to remove important impurities such as oxides and sulfides which may have been present in the ingot. Simply described, electroslag refining comprises a metal ingot positioned over a pool of molten ingot metal in a suitable vessel or furnace where the molten metal pool includes a surface layer of solid slag, an adjacent underlayer of molten slag and a lowermost body of refined molten ingot metal. The ingot is connected as an electrode in an electrical circuit including the molten metal pool, a source of electrical power and the ingot. The ingot is brought into contact with the molten slag layer and a heavy electrical current is caused to flow across the ingot/molten slag interface. This arrangement and process causes electrical resistance heating and melting of the ingot at the noted interface with the molten ingot metal passing through the molten slag layer as a refining medium to then become a part of the body of refined ingot metal. It is the combination of the controlled resistance melting and the passage of molten ingot metal through the molten slag layer which refines the ingot metal to remove impurities such as oxides, sulfides, and other undesirable inclusions.
In metal spray forming, a small stream of refined molten metal from the furnace is caused to pass concentrically through a molten metal spray forming atomizer generally comprising a closed peripheral manifold about a central aperture. The manifold is equipped with gas inlet means and plural gas jet exit means. An inert gas under pressure is supplied to the manifold to exit through the gas jets in converging streams which impinge the passing metal stream to convert or break up the metal stream into a generally expanding spray pattern of small molten metal droplets. This spray pattern is caused to impinge and deposit on a suitable collector surface to generate a metal billet or other metal object.
Best results are obtained when the molten metal spray pattern from the atomizer is directed angularly against the collector or preform object rather than perpendicular. An angular impingement provides improved deposition efficiency as well as improved preform metal density and microstructure. However, some collector preforms are of a size and shape which require the spray pattern to be directed at greater angles and some means is required not only to convert a vertical molten metal stream to a spray pattern, but also to angularly direct or adjust the spray pattern at these greater angles for corresponding angular impingement against various collector preforms.
Accordingly, it is an object of this invention to provide an improved molten metal spray forming atomizer for a molten metal refining apparatus in which the manifold ring is non-circular to have a greater range of transverse angular rotation without interfering with the molten metal stream passing therethrough.